Corn silk is a waste material obtained from corn that contains carbohydrates, proteins, and vitamins. Interestingly, corn-silk-derived carbon (CSC) after activation is found to possess larger specific surface area (2550 m 2 g −1 ) and appreciable pore volume (0.95 cm 3 g −1 ). In the present investigation, CSC electrodes are used to fabricate symmetric coin and pouch cells individually and investigated for electrochemical performance in half and full cell assembly systematically. Half-cell performance of CSC exhibits a maximum specific capacity of 256 mA h g −1 at 100 mA g −1 . The subsequently assembled symmetric coin type sodium-ion capacitor (SIC) delivers a maximum specific capacitance of 126 F g −1 at 0.3 A g −1 , and the pouch cell delivers 135 F g −1 at the same current density. Symmetric capacitors are found to withstand high current densities up to ∼3 A g −1 with nominal capacitance values, thus qualifying the suitability of CSC for SIC applications. A maximum specific energy of ∼109 Wh kg −1 and a specific power of ∼12.16 kW kg −1 have been realized from the symmetric SICs. Feasibility of the fabricated devices for practical application has been demonstrated by glowing LEDs and by running a clock for 25 min.

Metal sulfides have received tremendous attention as promising next-generation anode materials for lithium-ion batteries (LIBs) as a result of their high capacity, good mechanical strength, and low cost. Herein, we have exclusively designed an architecture by integrating NiS porous nanospheres and graphenesheet-like coir-pith-derived biocarbon via a simple, scalable, and low-cost one-pot synthesis technique. The porous nanosphere morphology of NiS and the complete wrapping of such nanospheres with coir-pith-derived carbon (CPC) are apparently evidenced through scanning electron microscopy, field emission scanning electron microscopy, and high-resolution transmission electron microscopy. The NiS/CPC composite exhibits superior electrochemical performance when tested as an anode for LIBs with high reversible specific capacity (650 mAh g −1 at 100 mA g −1 ), good cycling stability, high rate capacity (410 mAh g −1 at 2 A g −1 ), and better extended cyclability compared to its pristine counterpart (NiS). The observed superior electrochemical performance of the NiS/CPC anode is attributed to the presence of CPC that preserves the required structural and mechanical strength. For example, CPC acts as a cushion to effectively accommodate the volume changes upon cycling at higher current rates and improves the kinetics of the electrode reaction kinetics.

Layered NaLiTi 3 O 7 (NLTO) material synthesized by the sol−gel method has been qualified as a low voltage insertion anode for lithium and sodium ion batteries (LIBs and SIBs, respectively). Pristine NLTO anode material demonstrates the insertion behavior in the voltage range of 0.5−2.0 V in LIBs and around 0.1−1.5 V in SIBs. It delivers a specific capacity of 100 mAh g −1 in LIBs and 30 mAh g −1 in SIBs, thus indicating the necessity to improve the electrochemical performance. Accordingly, coir pith derived carbon (CPC) has been added to produce the NLTO/CPC composite anode. To the best of our knowledge, this is the first report discussing the anode behavior of biocarbon added NLTO material in LIBs and SIBs. Decoration of NLTO microparticles on CPC is performed by adopting a simple sonication method. Such a CPC added NLTO increases the specific capacity and demonstrates in LIBs to the extent of 160 mAh g −1 at 100 mA g −1 for 100 cycles. In SIBs, CPC improves the capacity of the NLTO anode marginally to ∼60 mAh g −1 up to 500 cycles. Hence, it is understood that NLTO/CPC finds its suitability in LIBs rather than in SIBs as probable anodes.